There are always fighters that get hyped, Pavlik is one of the few Americans that has a shot of dominating multiple divisions, does he have flaws? Absolutely, but he is a class act and makes for exciting fights.
Fanboyism is a side effect of having those credentials.

for further reading on fanboyism research, David Haye, PAC, Cotto (prior to Margarito) and Hatton (prior to Mayweather)

It's been a while since Americans have had someone that could be a dominant force and had the personality to get behind (second criteria excludes Mayweather)